To increase fuel economy, many vehicles have been switched over to front wheel drive so that the vehicle engine's weight can be over the main traction axle of a vehicle. To further increase fuel economy, many front wheel drive vehicles utilize a transverse mounted engine and transmission. To provide improved performance in inclement weather, many vehicles have selective four wheel drive capabilities. Typically in most front wheel drive vehicles with four wheel drive capability, the transmission powers a front differential. Torsionally downstream of the front differential is a power takeoff unit (PTU). The PTU couples the front differential with a prop shaft extending longitudinally to a rear axle and differential. To maximize fuel efficiency in selective four wheel drive vehicles, it is desirable to torsionally not only cut off the rear axle from the vehicle engine, but additionally causes the propeller (prop) shaft and most of the PTU to stop rotating. For quickest actuation/shift time for the demand of four wheel drive, the PTU requires some type of hydraulic actuation from a pressure source.
It is desirable from a cost standpoint to make the PTU fit as many vehicles as possible for a given manufacturer. Accordingly it is desirable to provide a PTU that can be hydraulically driven by different pressurized fluid sources. One source can be a hydraulic pump powered by an electrical system. Another embodiment can be an independent hydraulic pump driven by a belt off of an engine crankshaft. Still another embodiment can be the vehicle transmission pump, the power steering pump, or a pump driven by a gear on of the wheel axle. It is desirable to provide a PTU that is hydraulically powered that can be powered by a multitude of pressured fluid sources.